Cathode ray oscillograph



Nov. 25, 1941.l M. KNoLL 2,263,733

' CATHODE RAY OSCILLOGRAPH Original Filed Nov. 18,"1929 3 Sheets-'Sheetl INVENTOR.

` l Max Kwon. P165 A TTORNEY.

Nov. 25, 1941. M.\KN0L|.

v CATHODE RAY oscILLoGRAPH 3 Sheets-Sheet 2 INVENTOR. Max KNOLL .am .LEE5%8 w A TTORNE Y.

Nov. 25, 1941. M. KNoLL CATHODE RAY bscILLoGRAPH 3 Sheets-Sheet 3ATTORNEY.

Patented Nov. 25, 1941 oArnoDE RAY osoILLoGRAPH Max Knoll,Berlin-Charlottenburg,

Germany,

assignor to Radio Corporation of America, New York, N. Y., a corporationof Delaware Application February 5, 1935, Serial No. 5,136, now PatentNo. 2,152,487, dated March 28, 1939, which is a division of applicationSerial No. 408,006, November 18, 1929, now Patent No. 2,036,532, datedApril 7, 1936. Divided and this application February 25, 1939, SerialNo. 258,528

(Cl. P18-7.2)

6 Claims.

This invention has for its object improvements in cathode-rayoscillographs, and is a division of my copending application,lSerial No.

5,136, led February 5, 1935, which issued as Patent No. 2,152,487 onMarch 28, 1939, and which was a divisional application of Patent No.2,036,532, which issued April 7, 1936.

According to the invention special means are provided in order to keepthe focus, so long as it is not moving at its great recording orscanning speed, diverted from the window or other electron beamreceiving member. This may be `effected in a manner known per se, bydiverting the electronic rays sideways by Vmeans of a constant magneticor purely electrical eld, or a combination of both. Preferably a plateof beryllium or other substance of low atomic weight may be arranged,against which the rays strike during their diversion, in order toprevent as much as possible the generation of X-rays.

`For the further protection of the observer and of the photographiclayer against X-rays this plate is in turn covered with an envelope ofmaterial of high atomic Weight, e. g. lead.

`According to the invention the protection of the window may be effectedby intercepting the electron rays instead of diverting them, i. e. byarranging in the path of the electronic rays a beam intercepting meansin the form of a boredthrough negatively charged stopping-electrode, thenegative charge of which is let off at the beginning of the recordingoperation. As the cathode-ray oscillograph which is the subject of theinvention is intended to be used for rendering visible or recordingextraordinarily rapidly occurring phenomena, or for television purposes,the switching on or o of the diverting or stopping device has to beeifeeted in an extraordinarily short space of time, e. g. in 10-6 sec.'Ihis problem may be solved by a purely electrical switching device withtwo stable positions of equilibrium, e. g. by the employment of electrontubes, glow-lamps or spark gaps. The invention provides for .thispurpose a specially simple and, rapidly reacting electrontube device,which is actuated simultaneously with the start of the voltage to berecorded by the oscillograph. In this .way the voltage of thegrid-potential of another valve (the so called dei-lector" tube) can atthe same time be maintained at the same value, and its saturationcurrent made to ow through a condenser connected in parallel with thecontrols, the voltage of which is thus varied proportionally with thetime.,

With apparatus for picture-telegraphy or television in which the wholearea of the picture both in transmitter and receiver is scanned by thefocal spot in a zig-zag path consisting of upward and downwardstraight-line branches, one set of branches, say the upward, can bedescribed at a constant relatively slow velocity, and the other set, thedownward, at a constant relatively high velocity by suitably varying thecontrol voltage, as by charging or discharging inserted condensers bymeans of a constant current, e. g. the saturation current of electrontubes. This must be eifectedby employing two different constantintensities of current. Thus only the one set of parallel branches isValid for the chemical and physical effects, in contrast to the hithertoused sinusoidal records, in which, on each of both branches, therecording velocity and the distance from the neighboring branch arecontinually changing( The cathode-ray oscillograph forming the subjectof this invention can be used in picturetelegraphy and television andalso in the transmitting station for scanning the picture to betransmitted, and further for frequency multiplication for secrettelegraphy and the like by scanning separated electrodes arranged inchecker board fashion behind the window and easily exchangeable.

Since neither for transmission nor reception need any mechanical partsbe moved, the new -cathode-ray oscillograph, especially forpicturetelegraphy and television olers a number of such importantadvantages as to enable both these operations to be carried out withhitherto unattainable perfection.

The synchronization which must be maintained between transmitting andreceiving apparatus, is obtained with the utmost ease and with absoluteexactitude by simultaneously affecting the corresponding controls of thetransmitter and the receiver by the voltage either directly by wire, orindirectly by wireless waves.

The recording velocity obtainable is so great that e. g. a picture of 6x 6 cm. Ymay veasily be scanned in 1/1000 sec., or even in 1/10000 sec.,and reproduced with suicient intensity. V i

If a picture-frequency of not-more than 16 pictures per second (which isadequate forf the human eye) is required, pictures of such intensity maybe obtained, that they may be projected on a much enlarged scale on to ascreen and made visible to a large company of spectators. A

Cinematographic lms can be copiedY by 'vvir'eless transmission at anydistance.

The speed with which the pictures canbe scanned in the transmitterandreceiver makes it possible to scan, transmit, and reproduce in onecontinuous line pairs of stereoscopic pictures, so that either static'or in-proces's-of-production plastic picture-telegraphy Yand plastictelevision are made possible in the simplest manner by one and the sameapparatus.

The extraordinary speed with vwhich a picture can-be scanned at thetransmitting ystation and recorded -atl thev reception station, and thepossibili-tyl ofextremely rapid withdrawal of the -focusafter the-picture has been completely scanned; enable also the transmitting andreception devices to be used for super-speed recording of. slow motionpictures, in which case a much-greater number Aof pictures per secondAcan easily be recorded, than has been possible with slow-motionapparatus hitherto used. If a very high number of picturesper second isto be obtained', it is, for'instance, only necessary, firstly,l in thereceiving appartaus, to double the length of the' picture, that is tosay the sum of the intervals between all the branches of thezigzag'pathyso that with a stationary photographic plate one wouldobtain a distorted picturedouble the width; and secondly, to run thereceiving lm ,o

constantly at half speed. This gives the slow motion pictures,I theoptical compensation otherlWiseTequired being here` replaced by theYswift withdrawal of the focus.

The-invention is exemplied in the drawings.

Fig. 1 shows schematically a cathode-ray oscil- .log'raph; such as canbe employed for the various above `mentioned purposes.

Fig. 2 shows on a larger Yscale'-"schematically drawn-an example of thewindow ofa cathode- A'ray oscillograph 'used for the transmission' ofpictures-or for'televi'sion.

Figi 3 'shows a window ofthe same sort inthe receiving apparatus, forthe photographic Arecord of the wirelessly transmitted picture.

Fig. 4 shows schematically, lhow `the'cathode'- ray tube of thetransmitter'and the cathode-ray 'tube of the'receiver work together inpicture telegraphy or television. Y

Fig. 5 shows'ona larger scale a vacuum-proof pliable device for shiftingmovable parts, such as,

duction vofoscillations with -linear variations of n voltage-as usedespecially for televisional or picture telegraphicI apparatus.Y

Fig. 9 shows the wave-shape of the linear oscillations prduced by meansof such a connection.

In the cathode-ray oscillograph represented` in Fig. 1 the cathode-raybeam is produced in the metallic discharge-tube l, which serves at thesame time as an anode, and into which the cathode 2 is introduced bymeans of the bushing 3. The cathode 2 is connected with'the feed-voltageby means of the rod 3 lodged in the bushing 3. The coil 4 serves toconcentrate the ray beam before it passes through the narrow aperture ofthe diaphragm 5 into the actual diversionchamber 1 and onto theelectron-permeable window 6.

Asl electron-permeable substances the same materials may in general beused as were formerly employed for the Lenard tubes already mentioned.These are, first of all thin metal foils, e. g., aluminiurn,chromium-nickel, steel alloys, beryllium. Also-foils of insulatingmaterial, Celluloid, Cellophane, cellulose products, etc. may be used.Porous materials, such as paper, can also be used the pores of which arejust ne enough to oppose to the passage of gases a relatively high, andto that of electrons a relatively low, resistance. In the -latter eventthe slight quantity of gas admitted through the pores must of course beconstantly drawn off by an air-pump. Owing to their comparatively lowatomic weight, glasses may also be used, especially such with componentsof particularly low atomic weight, as for example the Lindemann glass sooften employed 'forrX-ray tubes, consisting of beryllium, lithium andboron.

In general it will be necessary to reinforce the thin foil required forthe purpose described by a framework to sustain the outer atmosphericpressure. This-framework may, for instance, consist of a Wire-netting,which may in its turn be reinforced by means ol" a bearing cross,supporting grid or the like. For the reinforcement of -the foil it ispossible also to employ a thin metal plate `perforated plentifully withsmall-holes. For the making of such a plate, appropriately perforated, anew process had to be devised. The purpose of the framework as employedin the invention is to make -it possible to use, for the window, foil ofextremest thinness, in order thereby to insure that the window shall bepermeable to the electrons to a corresponding maximum degree. Further,in the framework, the ratio of the total area of the perforations orapertures-of admission` to the total area of the non-perforatednonpermeable portion of the framework has to-be as great as possible.Furtherl also the apertures-of admission must lie as densely as possibletogether and be -of such small size, that the focal spot coverssimultaneously several adjacent apertures.

The making of such plates involves special'diculties. To make suchperforated plates the present invention employs a process similar tothat used in autotype printing -ior the making of the printing-blocks.As is known, it is possible, by means of stippling-prccess photography,-to engrave upon a surface adjacentlyat extraordinarily minute intervals,dots of any desired form'-squar'e, for instance, the ratio of the Widthof the dots to the width of-the lines of the networkof clear spacesbetween the dots depending upon `the degree of illumination oflthephotographed surface. It is possible thus to cover a surface with anextremely dense network of dots of uniform size. Whereas, however in themaking of a printing-block the network of lines is etched into theblock, in making a perforated plate for-the purpose here in -view thenetwork-o1" lines is imprinted or copied on tothe -plategv-and thedot-surfaces etched through the plate. A'The line-work can also beengraved into the plate, the

lines of engraving covered with a protecting layer,

and the dot-surfaces lying between the lines etched through the plate.

The thin foil forming the window can also, instead of being reinforcedsubsequently by the grid, be made directly upon the outer surface of thegrid. For this purpose the holes of the perforated plate forming thegrid can be lled in with a substance which may be later on removed (forinstance, wax, parain), and a thin layer, e. g. of beryllium, iron, orsilicum, deposited galvano-plastically or by cathode-sputtering over theentire outer surface of the plate. A thin layer of some acid-proofsubstance such as gold, for instance, can be deposited on the `plateprevious to perforation and the holes then etched out in the manneralready described. In this way are obtained an extraordinarily intimatevacuum-proof connection between foil and grid, perfect reinforcement,and `the maximum abduction of heat. The thickness of the foil can bereduced to as little as 1/1o,ooo mm. So thin a foil would, unless by souniting it with the grid, be extraordinarily difficult, or practicallyimpossible to mount. Windows made in this way are permeable to electronsto a degree hitherto never even remotely approachable; they are,further, owing to the effective abduction of the heat, not liable to beburnt through; they are easy to make and to use; and thanks to theirperfectly plane form enable sharply dened photographs to be taken withordinary plates or films.

8, 8 are the deflector plates, which can be adjusted under a high vacuumwith the help of elastic bodies 9 or membranes I8 by means of Y screwsII, which are lodged in supporting tubes I2. `I5 is a spy-hole, throughwhich the oscillogram to be recorded can be observed also while thephotographic record is being taken, provided that the inner side of theelectron-permeable layer 6 or parts of the grid 19 are overlaid with aphosphorescent substance. The photographic layer V(plate or film I4) issituated during the taking of the record in the shutter I3.

Fig. 2 shows on an enlarged scale in section an example of aphotoelectric-cell arrangement for taking pictures. Close behind theelectron-permeable window 6, which is also held by the grid 19, issituated the photo-electric mosaic plate' 8l, which is subdivided bymeans of insulation-layers indicated in Fig. 2 by the short verticallines, into as many small fields or photo-electric cathodes aspicture-stippling points are desired. These small photo-electriccathodes forming the plate 8I are scanned successively by the electronicbeam passing rapidly across them, with the result that a current ofvarying intensity flows through the cathodes to the common grid anode82. VThus across each element is developed a potential having a valueaccording to the resistance effective at any given moment dependent onthe exposure of the cell in question. The developed potential betweenthe anode 82 and ground is supplied to the amplifier |06' as shown inFig. 4.

Instead of a photo-electric cell an exchangeable electrode arrangementof any desired formation can also be xed on the recording apparatusbehind the electron-permeable window, enabling a definite succession ofcurrent impulses to be sent out for'whichthe receiving apparatus must bearranged accordingly.

A simple method of transmitting pictures also consists in rstcopying thepicture according to a Vcertain process onto a metal plate in such amanner that definite conductivity-values at different points of thesurface of the metal plate correspond to the varying intensities oflight on dierent parts of the picture. For example, the picture on themetal plate may be a photographic reproduction in carbon or other`resistance substance, or a print made with resistance substance. Someforms of printing ink may havey sucient electrical resistance for thepurpose. The electronic beam passing through the electron-permeablewindow and the resistance image to the plate can excite directlyfluctuations of current in the ampliiier |96 (Fig. 4) which will serveto vary the intensity of the cathode-ray in the receiver.

A further possible method of application of the Ainvention topicture-telegraphy consists e. g. in

utilizing the travelling point of light produced outside thetransmitter-tube on the fluorescent screen over a system of lenses forscanning the picture to be transmitted and having the reflected raysgathered up by one single large photoelectric cell.

Fig. 3 shows on an enlarged scale in section an example of theconstruction of an electronpermeable layer 6 for cathode-rayoscillagraphs with a supporting grid 19 of metal strips placed edgewise.`The electronic beam when not in use falls behind one of the aluminumblades 83; the X-rays then generated are screened off by a lead mantle84. The oscillogram or picture appears on a iiuorescent layer fixed ontothe exterior side of the electron-permeable foil 6. If photographicrecords have to be made, the light sensitive film or plate I4 is pressedclosely onto the electronpermeable window E by means of the light-proofshutter I3.

Fig. 4 shows an example of an arrangement for a cathode-ray oscillographin accordance with the invention, applicable for picture telegraphy andtelevision, a denoting the receiver arrangement, b the transmitterarrangement; both are, wireless transmission being pre-supposed,connected with each other by way of antennae 9| and 9|. For sending andreceiving there serve respectively the cathode-ray oscillographs 92 and92 with hot-cathode discharge devices 93 and 93 respectively, pairs ofdeflector plates 94', 95 and 94, 95 for producing a scanning movement ofthe cathode-ray beams of the respective oscillographs andelectron-permeable windows 6 and 6. The pairs of deflector plates 94',95', and 94, 95 respectively shown in the diagram for the sake ofclearness as parallel lie in the actual apparatus in each tube in planesat right angles to each other. The feed voltage for the discharge tubeslies at points 91', 98', and 91, 98 respectively.

By means of intercepting-electrodes 99 and 99 respectively, arrangedbetween the hot-cathodes in the tubes 93 and 93 respectively, and thecorresponding anode 91 and 91, the generation of electronic-rays duringthe pauses in the scanning movement as controlled by plates 94 andthereby the fusing of the window, is prevented in a manner to behereinafter described. The electrons passing through the electronpermeable layer 6 of the transmitter tube 92 fall upon a photo-electricmosaic of known construction |90, the photo-electrically active layer 8Iof which is divided in a manner known per se (for example, as disclosedin Patent No. 1,691,329 to Zworykin dated November 13, 1928, and ePatent No. 1,780,364 to Reynolds dated November 4, 1930), into a largenumber of small separate areas shown enlarged in Fig. 2. On thephoto-electric `layer .thereis formedbyzmeans of lenses lll-liaocordingtothe :known laws ofoptics, a picturelof the .object t0-2 :to bereproduced, fso that :there Ifallsvupon eachof :the areasa.definite,.in,gen

reralvarying intensity. of light. Theillumination of leach farea takes:place vthrough `the widemeshed Mgrid y82, which .serves .as commonanode:for all the small .photo-electric cells. VThe'actual transmission iseffectedlby means Lof the .highlfrequency*transmitter1123, of. any known.or suitable form' `for multiple signal transmissiongas :for examplethatdescribed 1in the Zworykin ypatent Y.above referred to, and providedwith .a common transmitting antennae "9 and modulated in known manner bythe oscillators |04 .and |05 .as well as by the `luctuationso'l thephoto-electric cells/8| conducted .bywayofiamplier |86.

.Both oscillators |04 fandflilproduce, byfrneans .of :a'device known perse, and represented dia- -grammatically in Fig. 8, oscillations witha'timeproport-ional voltage-variation ofthe vwave-shape sketched inFig.9. In th-is manner there istinsured, in contrast to what happensnzthecase -,pair of delector plates 95 of the transmitter tube 92', and aretransmitted by way ofthe Yhighfrequency transmitter |03, the.transmitting antenna'S'l, the receiving antenna 9|,` and theselectiveamplifier |05 operating in known man- .,ner Vas for example theselective amplifier lil- 1| vof the Zworykin patent above referredto,xto the pairfof platesif95 of the receiver tube :92. When oscillator|05 is alone working, the scanning sweep or loscillations of theelectronic beam describe a .stationary line-equal 'to the height ofthepictureto be transmitted, both inthe trans- -mitter .tube andreceiver tube.

vIf-now the `deilecting or. sweep circuit oscillator |04 is `falsoswitched on (frequency ,about 103 per sec.), which effectsthesecondgpair yof'deflector plates :94' standing at right angles'to 95of the transmitter tube, theseoscillations aare transmitted `by .way ofthe same `path as those from oscillator'l, through a selective ampli-'er |94, tothe pair of deectcr plates-S4 of the receivertube 532 and theoriginal line -isonce again, transformed into a progressive'zig-zagrecord. If the frequency of the :oscillator |-04.is properly adjusted,the record produced has the Width of the Apicture transmitted. If rinIaddition the sweep of theoscillator |05 is not great- -er than aboutthe height ofthe line described by the focus spot, each point of .thepicture being transmitted, both in the transmitter tubeand in vthereceiver tube, is :scanned simultaneously and ffor'an equalV period bythe cathode-ray beam.

Theinterception of the electronic beam when .not being used is hereeffected by means of the intercepting electrodes 99 and 99 respectivelyby way-of -a--not here shown-tip-action electron- .tube device similarto that represented in Fig. 7,

which is controlled by means of the :oscillator l |04 and the amplier|84 -which latter two elements produce the scanning movement ofthebeams. As the cathode-ray beam on its Yway through the transmitter tube92' meets with varying `degrees of resistance according to the CIIconductivity of .the photo-.electric-.cell with which 4it happens tobefin contact, uctuations .of `current take `place .corresponding to theoccurring differences of intensity. .These iuctuations are vtransmittedby Way of the amplier |06', `the yhigh :frequency transmitter |03', thetransmitting ,antenna ;9|', the receiving antenna 9|,.and

a selecting amplifier |96, onto the control grid '|11 `of the receivertube'92, .there giving lrise to corresponding iiuctuations of thebeam-intensity, which in turn cause the requisite fluctuations inintensity of the picture reproduced on the fluorescent screen 6.

vThe arrangement schematically represented in Fig. vfi-both thetransmitting and the reception apparatus-allows also in the simplestmanner possible of transmitting stereoscopic pictures to any-,distanceand likewise of stereoscopic television. .A .stereoscopic picture, as iswell known, consists of a pair of-pictures side by side, representingrespectively the right and left eye views of a scene or object. If theWindow 6 :and 6 are made so long in one direction, e. g. ina directionperpendicular to the plane of the drawing, that a Ap-air of stereoscopicpictures can be scanned .adjacently and adjacently reproducedin thereceiver, then both pictures may be scanned by the focal .spot in onecontinuous line in each of both apparatus. The stereoscopic transmissionof pictures and stereoscopic television may be thus realized by simplytransmitting as a single picture, apair of stereoscopic pictures side byside. The pair of stereoscopic pictures thus received side by side atthe receiving station may be synthesized in known manner.

InFig. `5'is exemplied on -a larger scale the pliable device shown inFig-.1 employed for shifting movable parts under a high vacuum. The

device here serves for the adjustment of the elec- Vtrostaticdecctor-plate 8, by means of the pliable metal body V9 actuated by nut|01, pressing upon the carrier-bush 24. This vis joined by means ofthr-ee screws 25, sliding in slots of the jacket 25,

with the guide-ring 2l, into which, lby means of an insulating washer29, e. g. of Bakelite, is fixed `the supporting rod 28 of the deilectorplate 8.

Then-pliable body 9 is joined in a vacuum-tight .manner at both endswith its guide-rings, and

likewise the insulating washer 29 with guide-ring 21; furthermore, thesupporting rod 28 is guided by .another perforated insulating washer 30.The ring 3| `carrying washer -3EJ- is yixed directly into the jacket 1of the cathode-ray tube.

yThe vtube 32 for auto-electronic discharge shown -in Fig. 6 containsananode 33 andan intercepting electrode (auxiliary anode) 34 which duringtherelease of the `beam functions Ivas anvanode. The release is effectedby two spark wardly therethrough, thus maintaining the condenser `43charged-with the llower plate positive andthe upper plate negative. Ifthe gaps 35 and .36 are properly adjusted, any sudden surge of voltagearising from the transmission line or antenna v44 andinducted from the.winding 45 according tothe .polarity of the surge, either onto theIwinding 31 -or.38, .causes a sparking of `the gap 35 or 36, thedura-tion of which depends upon the value of the capacity 46 andtheresistance 41. By this the electrode 34, which has hitherto interceptedthe beam, becomes an anode, and the extremely sharp point of the cathode40 -ejects an electronic beam through the perforations in the electrodes34 and 33, the intensity of the beam can further bevaried by means ofthe controlling electrode 33 by varying the angle of the coneshapedelectronic beam. Y

In thelower part of Fig. 6 is shown schematicallyan electrostatic deviceforjconcentrating the electronic beam. It consists' of cylindrical metaltubes 48, sustained bysupports 49jin such a position asl to allow oftheelectronic beam passing freely through it, and of the metal ring washers50 between the tubes 48. If the `washers 502 are charged negatively tothe tubes 48,. divergentl electric fieldsl are formed, which exercise aforce concentrating radially the beam. Thus an exceptionallyminutefocal" spot is obtained. Adjustment of the voltage applied totheV tubeand washer elements at the polarity indicated inthe diagram, andaccording to the spacing of the electron-permeable window will bringthe' rays to a focus at the window, as will be understood by thoseskilled in-the a-rt.

The thermionic cathode-ray tube l shown in Fig.` '1, isprovided withthehot cathode-52, anode 53, andcontrol-grid 54 controlling the intensityof the electronsv in the beam while 4the latter is working. In order toprevent thev fusing ofthe window during periods when the focal spot isat rest, an intercepting electrode 55 is provided, actuated by atip-action electron-tube device. This'device consists" of theelectron-tubes 56, 51, and 58, the anodes of which are connectedl on theone hand by way of resistances` 56 and 60 with the positive pole of astorage battery, and on the other hand-crosswise-by way ofcondensers 6|,62 with the grids of the tubes 56 andl 51. Thusfar the circuitarrangement isquite similar to the `well known multivibrator circuit.However, in the present system thecircuit is; intended to function notas a multivibrator, 4but as a trigger or` tip-acting device forreleasing the blocking charge on the intercepting electrode 55. Thischange in the function is accomplished by substituting for the usualgrid leak between grid and cathode, a battery 63, which by way of thehigh resistances 64, 65 keeps the condenser 6| charged to the potentialof the battery 63 and the grid potential of the tube 56 at a lower levelthan the anode potential of tube 51, the amount of the diminution beingabout the same as the anode potential itself so as to bring the saidgrid potential to zero or negative. The potential between the grid andfilament of tube 56 will be the algebraic sum of the potential of theanode of the tube 51 and the battery 63. If the grid of the tube 51,which tube is fully emitting during the interception of the cathode-raybeam, is affected by a surge of negative voltage issuing from theantenna or transmission line 66 by way of the resistances 61 or 68, andby way of the condenser 69, the arrangement tips over into its otherposition of stable equilibrium. In that case tube 51 is blocked. IIhegrid potential of tube 56 and therewith that of the interceptingelectrode, hitherto negative, now receive the same potential as hotcathode 52, or a potential positive to it due to the rise in potentialacross the terminals of tube 51, and the cathode-raybeam is released. Ifthe surges issuing from the antenna or line 66 are positive, the tube 58acts in the same manner.

By means'ofresistfance 16, theA time of the tip# ping-over of the deviceback into the position of equilibrium corresponding to the period ofinterception of thecathoderay beam maybe adjusted at will", thusenabling the releaseto bemaintained for any length ottime desired.

Fig. 8 refersto adevice suitable for the production of oscillations withlinear variation of voltage, s uchhas' is provided' for thel oscillators|04 and |05' in Fig; In Fig. 8', 1l and 1|" are triode valves, fedlbythe batteriesy 12 and 12. By the saturationecurrent ofl these valves',the condenser 13'is alternately charged and discharged by wayofthe-resistances 1"4and 14. The charging and discharging isautomatically controlled by the gridsA 16 and 16"', the potential ofwhich is maintained at a suitable level by means of batteries 15 and15".Byvarying the capacity of the condenser 13, the; required frequency mayeasily and swiftly be obtainedwhen working.

If'the saturation-currents'of the valves 1'I and 1H are Wselectedait/various` values, or the resist'- ancesj14 and 14" are givendiierentA resistivities, the upward branches' 11 of the' oscillationstaking place proportionally with the time (see Fig. 9)' becomelesssteep-than the downward branches 16', whereby'both4 in the transmitterand in the' receiver-the eiect` of the downward branches is diminished*in comparison with that of the. upward branches;

If the batteries 15l and 1.5 shown in the connection-scheme` Fig'. 8Aand' their connections are omitted the gridl 16' joined' with the hotcathode' of its tube, and the grid' 16 effected by the voltagev of acontrol ofv the cathode-ray oscillograph, e'. g. bytliievoltage of theoscillator |65 showny in Fig; then to accumulate a definite chargeaftera given number of impulses from theoscillator' I'05, apositivedependence is obtained of the control' voltage 1.04' upon the Voltageof" theu control |05".V That is to say,` the lengthwise return ofthevfocal spot occurs always after adeiinite number of transverseoscillations.

1^. A transmission system comprising acathode ray oscillograph havingmeansto produce a beam of'A electrons, means" to deflect the beam ofelec# trons, an electron permeable window lying in the path of said beamof electrons, means to direct the beam of electrons through said window,a picture area electrode behind said window outside of said oscillographand immediately adjacent thereto, said electrode being adapted to bescanned by electrons passing through said window, means for derivingfrom said electrode electric potentials produced by thescanningelectrons which vary in accordance with the light and shades ofthe elemental areas of the picture area, a second cathode rayoscillograph having a focused beam of electrons, means to deiiect thefocused beam of electrons of said second oscillograph synchronously withthe deiiections of the beam of electrons of the first namedoscillograph, and means to vary the intensity of the focused beam ofelectrons of said second oscillograph in accordance with the derivedpotentials from said picture area electrode.

2. A transmission system comprising a cathode ray oscilloscope havingmeans to produce a beam of electrons, means to deect the beam ofelectrons, an electron permeable window lying in the path of said beamof electrons, means to direct the beam of electrons through said window,a light sensitive electrode behind said window outside of saidoscilloscope and immediately adje,`

cent thereto, said electrode having a picture area and being adapted tobe scanned "by electrons passing through said Window, andV means forderiving from said electrode electric potentials produced by thescanning electrons which vary in accordance with the lights and shadesof the elemental areas of the picture area.

3. A transmission system comprising a cathode ray oscillograph havingmeans to produce a beam of electrons, means to deflect the beam ofelectrons, an electron permeable Window lying in the path of said beamof electrons, means to direct the beam of electrons through said window,a metal plate electrode `having different conductivity values atdifferent points corresponding to the varying lights land shades of apicture, said electrode being positioned behind said Window outside ofsaid oscillograph and immediately adjacent thereto andfadapted to bescanned by electrons passing through said window, means for derivingfrom' said electrode electric potentials produced by the scanning.electrons. which vary in accordance .with the lights and shades of thepoints-of the picture, a second'cathode ray oscillograph having afocused beam of electrons, means to deflect the focused beam ofelectrons of said second oscillograph synchronously with the deiiectionsof the beam of electronsof the first named oscillograph, and means Vtovary the intensity of the focused beam of electrons of said secondoscillographin accordance with the derived potentials of said metalplate electrode.

4. A transmission system comprising a cathode ray oscillograph, means to`produce a beam of electrons, an electron permeable Window lying in thepath of said beam of electrons, means to direct the beam of electronsthrough said Window, means to deflect the beam of electrons over thearea of said window, a plate having a picture formed of electricalresponsive material on one surface of said electrode, said electrodebeingr positioned behind said window outside of said oscillographandimmediately adjacent thereto with the picture facing saidwindovv,said'picture being adapted to be scanned, by ffelectrons passing throughsaid window, vmeans for deriving from said plate electricpotentialsproduced by the scanning electrons which vary in accordance with thelights and shades of the elemental areas of the picture, and an outputcircuit to receive the derived potentials.

5. A transmission system comprising a cathode ray oscillograph, means toproduce a beam of electrons, an electron permeable Window lying in thepath of said beam of electrons, means to direct the beam of electronsthrough said Window, means to deflect the beam of electrons over thearea of said Window, aplate having a permanent image formed ofelectrical responsive material on one surface of said electrode, saidelectrode being positioned behind said Window outside of saidoscillograph and immediately adjacent thereto with the permanent imagefacing said Window, said permanent image being adapted to be scanned byelectrons passing through said window, means for deriving from saidplate electric potentials produced by the scanning electrons which varyin accordance with the lights and shades of the elemental areas of thepermanent image, and an output circuit to receive the derivedpotentials. Y

6. A transmission system comprising a cathode ray oscillograph, means toproduce a beam of electrons, an electron permeable window lying in thepath of said beam of electrons, means to direct the beam of electronsthrough said window, means to deiiect the beam of electrons over thearea of said Window,.a plate having a predetermined optical image formedof electrical responsive material on one surface of said electrode, saidelectrode being positioned behind said window outside of saidoscillograph and immediately adjacent thereto with the predeterminedoptical image facing said window, said predetermined optical image beingadapted to be scanned by. electrons passing through said Window, meansfor deriving from said plate-V electric potentials produced by thescanning electrons which vary in accordance with the lights and shadesof the elemental areas of the predetermined optical image, and an outputcircuit to receive the derived potentials. l Y y MAX KNOLL.'

